Is Trillion A Real Number?

Merrian-Webster dictionary defines trillion as an indeterminately large number. But following the logical sequence of naming numbers trillion would be after billion. I know that numbers have no end, but does the true name of them have one? Is the sequence of billion, trillion, quadrillion, and quintillion just made up because it is logical? After all it is used a lot in everyday speech such as we are a trillion dollars in debt.